1. Field of the Invention
The present invention concerns a ship whereof the stern is equipped with a device for deflecting a flow of water.
It more particularly concerns a ship with large dimensions and a high tonnage, such as a cruise ship in particular, the displacement speed of which is relatively limited in relation to that of light and fast boats, this speed being between 10 and 25 knots or approximately between 18 and 45 km/h in cruising speed, for information, and the Froude number of which does not exceed 0.28.
2. Discussion of Related Art
It is known to equip the hull of a ship of this type with a deflector member in wedge form, positioned below the waterline, in the connection zone of the bottom of the hull with the rear flank—or bow—of the ship.
The function of a deflector of this type, generally designated by the expression “trim wedge”, is to deviate, downward and rearward, the flow of water in relative movement, which passes under the hull, at the stern, which results in increasing the power of the ship or, correlatively, by decreasing the fuel consumption necessary for its propulsion for a given speed.
A deflector of this type is described in patent U.S. Pat. No. 6,038,995, for example.
One drawback of the known deflectors is that their efficiency, in particular regarding power gains provided, depends on the trim of the ship (which can depend on its load and/or navigation conditions), as well as the ship's speed.
The dimensions and the angle of the “wedge” making up the deflector, which are determined in order to ensure maximum effectiveness under certain given trim and speed conditions, are therefore not necessarily optimal under other conditions.
Already known from document WO-98/24684 is a small fast motor vessel, provided at its rear end with two pivoting float bodies, arranged on either side of the propulsion means of the boat.
These float bodies are deployed downwardly, when the boat moves at a low speed, so as to lift the rear of the boat, cause it to squat (passage into plane mode) and thereby decrease the shoulder wave at the front of the ship.
At high speed, the float bodies are on the contrary in the withdrawn position.
This type of arrangement of the hull is not, however, applicable to a ship with large dimensions and high tonnage, which does not squat. Moreover, it does not make it possible to avoid the recirculation of the wave at the rear of the ship, whereas this phenomenon is the source of a loss of propulsive energy for the ship (through increased friction and disruption of the flow in the vicinity of the blades of the propulsive means).
Moreover, this type of float body does not make it possible to resolve the problem of rear slamming, as the surge coming from the rear can freely penetrate under the rear counter, in the central zone of the boat which extends between the two float bodies.